🌡️ Temperature

Temperature Converter

Celsius to Fahrenheit for the weather, Kelvin for the laboratory, Rankine for engineering — all handled with exact formulas. Press Convert after entering your value.

Written and reviewed by SM Arijul Islam · Last reviewed 28 October 2026 · Editorial standards · Report an error

Temperature conversion formulas

°C = (°F − 32) × 5/9
°F = (°C × 9/5) + 32
K = °C + 273.15
°R = (°C + 273.15) × 9/5

Oven temperature chart (gas mark, °C, °F and fan oven)

Gas mark to Celsius, Fahrenheit and fan-oven temperature conversion chart
Gas mark	°C	°F	Fan oven °C	Typical use
¼	110	225	90	Very slow, drying
½	120	250	100	Very slow, meringue
1	140	275	120	Slow, rich fruit cake
2	150	300	130	Slow
3	160	325	140	Warm, biscuits
4	180	350	160	Moderate, sponges and cakes
5	190	375	170	Moderately hot, pastry
6	200	400	180	Moderately hot, roast chicken
7	220	425	200	Hot, scones and pies
8	230	450	210	Hot, bread
9	240	475	220	Very hot, pizza

Gas marks and Celsius figures are approximate. The °C column lists the rounded dial settings printed on UK recipe charts rather than an exact conversion of the °F column, oven thermostats vary by about ±10 °C, and a fan (convection) oven usually needs the temperature turned down by 20 °C or the baking time shortened by 10–15 minutes.

Everyday reference points

Water freezes at 0 °C / 32 °F / 273.15 K
Water boils at 100 °C / 212 °F / 373.15 K at sea level
Typical human body temperature: 37 °C / 98.6 °F
Absolute zero: −273.15 °C / −459.67 °F / 0 K

Technically no temperature can go below absolute zero, so negative Kelvin results are mathematically valid but physically impossible.

How to convert temperature

Temperature scales differ in both their zero point and their step size, so unlike length they cannot be converted with a single multiplier. Celsius and Fahrenheit have different zeros and different degree sizes, Kelvin starts at absolute zero with the same step as Celsius, and Rankine uses Fahrenheit-sized degrees above absolute zero. That is why this converter applies a separate formula in each direction rather than a factor.

Common temperature conversions

Common temperature equivalents across Celsius, Fahrenheit and Kelvin
Temperature	Equivalents
0 °C	32 °F · 273.15 K
20 °C	68 °F · 293.15 K
37 °C	98.6 °F · 310.15 K
100 °C	212 °F · 373.15 K
−40 °C	−40 °F · 233.15 K

Everyday uses

Weather forecasts and international travel
Cooking, baking and food safety
Science, laboratories and engineering
Body temperature and fever checks
HVAC, refrigeration and heat pumps

Temperature is not a linear scale like length. Use the Convert button to apply the correct formula rather than a simple factor.

Frequently asked questions

How do I convert Celsius to Fahrenheit?

Multiply by 9, divide by 5, then add 32. For example, 20 °C becomes 68 °F.

What is absolute zero?

0 K, which is −273.15 °C or −459.67 °F — the point at which molecular motion is minimal.

Is 0 °C the same as 0 K?

No. 0 °C is 273.15 K. Kelvin starts at absolute zero, far below water's freezing point.

Why is −40 the same on both scales?

Because the two scales cross at that value: −40 °C equals exactly −40 °F.

What is gas mark 4 in Celsius?

Gas mark 4 is 180 °C / 350 °F in a conventional oven, or about 160 °C in a fan oven. The chart above lists every gas mark from ¼ to 9.

How do I convert an oven temperature for a fan oven?

Subtract 20 °C from the conventional figure, since a fan moves heat more efficiently. 180 °C conventional becomes 160 °C fan, and 200 °C becomes 180 °C fan.

More worked examples

A recipe calling for 180 °C needs 356 °F on an American oven dial: 180 × 9 ÷ 5 + 32.
A fever of 38.5 °C is 101.3 °F.
A laboratory reading of 300 K is 26.85 °C.
−40 °C and −40 °F are the same temperature — the one point where the scales cross.

Oven and everyday temperatures

Common oven and everyday temperatures in Celsius and Fahrenheit
Celsius	Fahrenheit
150 °C	302 °F
180 °C	356 °F
200 °C	392 °F
220 °C	428 °F
37 °C	98.6 °F
0 °C	32 °F

Common mistakes to avoid

Converting a temperature difference with the absolute formula. A rise of 10 °C is a rise of 18 °F, not 50 °F.
Assuming 0 °F equals 0 °C. Zero Celsius is 32 °F; zero Fahrenheit is about −17.8 °C.
Adding 273 rather than 273.15 when converting to Kelvin — close enough for cooking, not for science.
Forgetting that Kelvin has no degree symbol and never takes a negative value in ordinary use.

Further questions

What is the Celsius scale based on?

Historically the freezing and boiling points of water at standard atmospheric pressure, set at 0 °C and 100 °C.

Can absolute zero be reached?

No. The third law of thermodynamics says it cannot be reached in a finite number of steps; scientists have approached it to within a tiny fraction of a kelvin.

How much is a change of 1 °C in Fahrenheit?

1.8 °F. Only the step size changes between scales, not the zero point, for differences.

Which countries still use Fahrenheit?

Mainly the United States, along with some informal use in a few other places; most of the world uses Celsius.

Sources and standards

The kelvin is defined by fixing the Boltzmann constant, and the practical scale used to calibrate real thermometers is maintained by the BIPM's Consultative Committee for Thermometry. The offsets on this page come from those definitions, not from rounded rules of thumb.

Fahrenheit to Celsius

To convert Fahrenheit to Celsius, subtract 32 and multiply by 5/9: 350 °F becomes (350 − 32) × 5/9 = 176.7 °C. For an oven, that is the moderate setting; a fan oven should then be set about 20 °C lower.

Fahrenheit to Celsius values used most often
°F	°C	Context
32 °F	0 °C	Water freezes
68 °F	20 °C	Room temperature
98.6 °F	37 °C	Body temperature
212 °F	100 °C	Water boils
350 °F	176.7 °C	Moderate oven
450 °F	232.2 °C	Hot oven

There are dedicated pages for Fahrenheit to Celsius and Celsius to Fahrenheit if you only need one direction.